Tesla Motors has now delivered more than a dozen of its sporty electric Roadsters, the company said in a newsletter this week.

It also is accelerating production. According to the newsletter released Wednesday night, 15 so-called "gliders" - cars equipped with everything but the battery and powertrain - have been completed at the Lotus assembly plant in Hethel, England, and are ready to be shipped to the Tesla offices in Menlo Park, Calif., where they will be finished.

The company in May said its production had been slower than expected, with only five of the $100,000 Roadsters completed in two months, instead of the one per week initially expected (see Tesla Production Slower Than Expected). The company said then that it planned to ramp up to 100 cars per month by November.

"In large measure we deliberately limit the production until we install our own born-and-bred final transmission by mid-September, at which time production will start to ramp up leading toward a monthly rate of over 100 cars in December," he wrote.